Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$245.75	7.795%	$264.9062	$264.91	$264.90	$264.90
Purchase #2	$37.48	3.614%	$38.8345	$38.83	$38.85	$38.80
Purchase #3	$217.82	3.454%	$225.3435	$225.34	$225.35	$225.30
Purchase #4	$12.66	8.355%	$13.7177	$13.72	$13.70	$13.70
Purchase #5	$209.49	9.553%	$229.5026	$229.50	$229.50	$229.50
Purchase #6	$88.49	11.240%	$98.4363	$98.44	$98.45	$98.40
Purchase #7	$242.83	4.430%	$253.5874	$253.59	$253.60	$253.60
7 purchase totals =	$1,054.52		$1,124.3282	$1,124.33	$1,124.35	$1,124.20